Dave reiterates my point, but illustrates that the Bay Lights switch varies in location with model and year. On our '06 Monterey it's among a row of switches on the entry wall below the passenger side dash.
Sometimes I'm reluctant to comment about the obvious for fear of insulting someone's knowledge, but the master rocker switch being off comes to mind as a #1 reason all the bay lights are unresponsive. I guess it's possible your coach doesn't have one, or at least not in an obvious place, but after 9 years I'd think you'd have seen it if it was placed like most of ours is. You may need to look harder for it. Hopefully someone else here with an '03 Monterey can help.
Joel